Problem on confirmation email - activation: MAIL HAS NOT BEEN SENT.

Hello,
I have a problem with activation email, my website can not send email confirmation to new members to validate their account.
If a new member who registers for my site displays the following error message:
MAIL HAS NOT BEEN SENT.
UNFORTUNATELY WE COULD NOT SEND THE CONFIRMATION E-MAIL TO YOU AT THIS TIME. PLEASE, TRY LATER. WE APPOLOGIZE FOR ANY INCONVENIENCE. PLEASE REPORT THIS BUG TO THE ADMINISTRATOR.

And so I do not received reports of cron job for over two days and the problem started the same day, I think there is problem on my mail server?
Or my site was changed?

Ask your hosting company or provider about this.

Or if you have your own VPS, check your cron jobs and mailer to see if there are any changes (settings).

Good luck

Do you have the SMTP module installed?